detected in the wheat cultivar ‘Lemhi’ to the barley attacking form of yellow rust, P. striiformis f. sp. hordei. Two major genes, as well as an undetermined number of minor genes, have been identified as responsible for this resistance in ‘Lemhi’. The present study aimed at quantifying and mapping those genes using QTL (quantitative trait loci) mapping procedures. For that purpose, an F2 population of 114 individuals resulting from the cross of resistant ‘Lemhi’ with ‘Chinese 166’, a wheat cultivar susceptible to barley yellow rust, was used as the mapping population. QTL effects and significance were estimated by means of interval mapping and MQM mapping procedures. In all individuals showing resistance towards P. striiformis f.sp. hordei, there was a visual chlorosis/necrosis response typical of race-specific, host resistance. QTL analysis resulted in the mapping of two major QTLs on chromosome arms 1DS (Psh1) and 2BL (Psh2) and two other, with a minor effect, on chromosome arms 5AL (Psh3) and 6AL (Psh4). Psh1 and Psh2 have been mapped to segments of the wheat genome where other wheat yellow rust resistance genes (Yr genes) and QTLs had previously been mapped, suggesting an association between host and non-host yellow rust resistance genes. The cloning of both major and minor Psh genes, as well as the Yr genes present in ‘Lemhi’, would allow us to determine the similarity of their structure and function. On the other hand, if a close linkage between major Psh genes and Yr genes is confirmed, it would suggest that these genes could have evolved from the same ancestral R gene. If that is to be the case, then their durability would be similarly perishable. The value of pursuing for non-host resistance genes as a source of durable resistance would therefore have to be seriously reconsidered.
Developing screening system for resistance to anthracnose in grapes by using culture filtrates from Elsinoe ampelina.
Hae Keun Yun*, Kyo Sun Park, Jeong Ho Rho, Youn Jung Choi, and Sang Bouk Jeong.
National Horticultural Research Institute, RDA, Suwon 440-706, South Korea.
This study aimed to show whether culture filtrates produced by E. ampelina are a substitute for pathogen inoculation or field screening of grape cultivars for anthracnose. Bioassays of grape leaves with culture filtrates showed that their phytotoxicities were active and host-selective. Ethyl acetate extracts from these also showed the toxicities and host selectivity among grape cultivars. The sensitive range of plants to culture filtrates of pathogen and their ethyl acetate extracts was consistent with the host range of the pathogen. Susceptible cultivars were sensitive to even highly diluted culture filtrates. However, resistant cultivars were not affected even by undiluted culture filtrates. Susceptible cultivars were more sensitive to the undiluted culture filtrates than highly diluted culture filtrates. This suggests that culture filtrates of the pathogen can be used as alternatives to pathogen inoculation or field tests in evaluating resistance to anthracnose in grapes.
Exploiting T. monococcum as a source of disease resistance traits to important UK fungal and viral pathogens
Dmitry Kornyukhin*, Kostya Kanyuka, Darren Lovell, Kerry Maguire, Jon West, O. P. Mitrofanova* and Kim Hammond-Kosack
Wheat Pathogenesis Programme, Plant Pathogen Interactions Division, Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK, * N. I. Vavilov All-Russian Research of Plant Industry (VIR), 42-44, Bolshaya Morskaya Str., 190000, St. Peterburg, Russia
Triticum monococcum is a diploid wheat with an AA genome. It is considered a rich source of novel genes and variant alleles. T. monococcum is accessible to wheat breeders as a gene/ trait source via established sexual crossing procedures. Many novel resistance loci are already known to reside within T. monococcum accessions. For example, novel resistance to eyespot (Cadle et al., 1997, Plant Disease 81; 1181-1186) and mildew (Shi, et al., 1998, Phytopathology 88: 144-1470). Alternatively, in hexaploid wheat several disease resistance loci of relevance to European agriculture were shown to reside on the A genome. For example, novel resistance to Septoria leaf blotch (Brading et al., 2002, Phytopathology 92: 439-445), and infection by Fusarium ear blight (type 1 resistance) ( Ban and Suenaga, 2000, Euphytica 113: 87-99.). The overall scientific objectives have been to assess the utility of the diploid wheat T. monococcum as a source of resistance to various fungal and viral diseases of importance in the UK. An initial collection of 124 diploid accessions were selected from stocks held in Russia, USA and UK. The VIR lines (n=26) were selected because they were known to exhibit resistance to pathogens and pests important in Russia. Seed were bulked at RRes and stock line purity examined by molecular markers. Most of the diploid accessions have been screened for their resistance and susceptibility to a range of commercially important pathogens to the UK. The focus was Soil-borne Cereal Mosaic Virus (SBCMV, genus Furovirus) transmitted by vector species Polymyxa graminis and disease caused by the non-biotrophic fungi, ie. Tapesia yallundae (eyespot), Mycosphaerella graminicola (Septoria tritici) leaf blotch and F. graminearum/ Fusarium culmorum, ear blight (FEB). These disease assays were undertaken in the glasshouse and also as small field plot experiments for S. tritici sown in both the autumn and the spring and for Fusarium spp from a spring sowing. For all the fungi and Polymyxa inoculations visual disease symptom assessments were made and for some pathogens their molecular identity was confirmed by PCR or ELISA. The main results show: 1. One VIR line exhibits root resistance to Soil-borne Cereal Mosaic Virus (SBCMV) (Kanyuka et al.,(2004): 154-160. Other resistant accessions will be reported. 2. No resistance to virus vector Polymyxa graminis was recovered. 3. Almost all the tested accessions were immune to Mycosphaerella graminicola (Septoria tritici)Fusarium ear blight infection. 5. The Tapesia screen is still in progress. In this poster we will provide details on these main findings and outline our intended future joint research activities. This research is sponsored by a Rothamsted Internal Fellowship award to DK. Rothamsted Research receives grant-aided support from the BBSRC.